Retrieval snare device and method

ABSTRACT

The present invention relates generally to devices and methods for retrieving or manipulating objects within a lumen. More specifically, embodiments of the invention relate to devices and methods for retrieving or manipulating medical devices from a body lumen. One embodiment of the present invention provides a novel and improved retrieval snare and method of fabricating and using the same. The snare includes a snare wire, having a distal end and a proximal end, for use in the human anatomy, such as but not limited to blood vessels, pulmonary airways, reproductive anatomy, gastrointestinal anatomy, and organs such as the kidneys or lungs. The device enables a user to capture a foreign object located within the human anatomy, grasp said object in a controlled manner, and retrieve and remove said object from the human anatomy.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/739,828, filed Jan. 11, 2013, titled “RETRIEVAL SNARE DEVICE ANDMETHOD,” now U.S. Patent Application Publication No. 2013-0184741-A1,which is a continuation-in-part of U.S. patent application Ser. No.13/475,819, filed May 18, 2012, titled “RETRIEVAL SNARE DEVICE ANDMETHOD,” now U.S. Patent Application Publication No. 2013-0184738-A1,which claims the benefit of U.S. Provisional Patent Application No.61/586,683, filed Jan. 13, 2012, titled “RETRIEVAL SNARE DEVICE ANDMETHOD,” all of which are hereby incorporated by reference in theirentirety.

INCORPORATION BY REFERENCE

All publications and patent applications mentioned in this specificationare herein incorporated by reference to the same extent as if eachindividual publication or patent application was specifically andindividually indicated to be incorporated by reference.

The following patents and patent applications are herein incorporated byreference in their entirety: U.S. patent application Ser. No.11/969,827, filed Jan. 4, 2009, titled “ENDOLUMINAL FILTER WITHFIXATION,” now Patent Publication No. 2008-0147111-A1.

FIELD

Embodiments of the invention relate generally to devices and methods forretrieving or manipulating objects within a lumen. More specifically,embodiments of the invention relate to devices and methods forretrieving or manipulating medical devices from a body lumen.

BACKGROUND

Embolic protection is utilized throughout the vasculature to prevent thepotentially fatal passage of embolic material in the bloodstream tosmaller vessels where it can obstruct blood flow. The dislodgement ofembolic material is often associated with procedures which open bloodvessels to restore natural blood flow such as stenting, angioplasty,arthrectomy, endarterectomy or thrombectomy. Used as an adjunct to theseprocedures, embolic protection devices trap debris and provide a meansfor removal for the body.

One widely used embolic protection application is the placement offiltration means in the vena cava. Vena cava filters (VCF) prevent thepassage of thrombus from the deep veins of the legs into the bloodstream and ultimately to the lungs. This condition is known as deep veinthrombosis (DVT), which can cause a potentially fatal condition known aspulmonary embolism (PE).

The next advancement in filters added the element of recoverability.Retrievable filters were designed to allow removal from the patientsubsequent to initial placement. These filters can incorporate retrievalfeatures that can be grasped and/or secured by a retrieval device, suchas a snare based retrieval device. Grasping the retrieval feature usinga snare generally requires the user to manipulate the snare over theretrieval feature, which can be difficult due to a variety of factors,such as retrieval feature geometry and location within the lumen, thestructure and properties of the snare, and ability to visualize theretrieval feature and/or snare using a real-time visualization techniquesuch as fluoroscopy.

Accordingly, it would be desirable to have an improved retrieval devicethat would facilitate engagement with a retrieval feature on a devicemaking retrieval and/or manipulation of the device easier and faster tocomplete.

SUMMARY OF THE DISCLOSURE

The present invention relates generally to devices and methods forretrieving or manipulating objects within a lumen. More specifically,embodiments of the invention relate to devices and methods forretrieving or manipulating medical devices from a body lumen.

One embodiment of the present invention provides a novel and improvedretrieval snare and method of fabricating and using the same. The snareincludes a snare wire, having a distal end and a proximal end, for usein the human anatomy, such as but not limited to blood vessels,pulmonary airways, reproductive anatomy, gastrointestinal anatomy, andorgans such as the bladder, kidneys or lungs. The device enables a userto capture a foreign object located within the human anatomy, grasp saidobject in a controlled manner, and retrieve and remove said object fromthe human anatomy. Examples of foreign objects which might be removedfrom the human anatomy include implants such as stents, guidewires,leads, sheaths, filters, and valves, and organic objects such as kidneystones or calcified emboli. Other areas where embodiments of the snarecan be used include, for example, removal and/or repositioning of distalprotection devices that are used in a variety of medical procedures suchas carotid stenting and percutaneous aortic valve replacement; andabdominal aortic aneurysm and thoracic aortic aneurysm devices. Forexample, a snare can be used to capture a vena cava filter and pull itinto a retrieval sheath for removal from the patient. The snare isadvanced through one or more retrieval sheaths, up to the site of adeployed filter. The snare is then deployed into the vessel, and engagedwith the filter. Finally, the snare is held under tension while thesheath is advanced over said filter, collapsing it into the ID of saidsheath. Another example is the use of a snare to grasp and extract loosekidney stones from a patient's kidneys. The snare is advanced throughone or more sheaths, up to the site of the loose kidney stone. The snareis then deployed and engaged with the stone. Next, the snare is pulledinto the sheath, drawing the stone into the distal ID of said sheath.

In some embodiments, a device for retrieving an object from a lumen isprovided. The device includes a sheath configured to fit within thelumen, the sheath having a proximal end and a distal end. A snare can bedisposed within the sheath. The snare can have a shaft with alongitudinal axis, a proximal end and a distal end and a plurality ofloop elements in connection with the distal end of the shaft. Theplurality of loop elements can have a collapsed configuration within thesheath and at least one deployed configuration outside the sheath. Theplurality of loop elements can be configured to be deployed through anopening at the distal end of the sheath. The at least one deployedconfiguration can include a fully deployed configuration in which theplurality of loop elements are deployed in a propeller-likeconfiguration.

In some embodiments, the first sheath includes a flexible distal tipportion that is configured to invert when the object is withdrawn intothe sheath.

In some embodiments, a plurality of sheaths includes flexible distal tipportions that are configured to invert when the object is withdrawn intothe sheaths.

In some embodiments, the plurality of loop elements in the fullydeployed configuration are angled less than 90 degrees with respect tothe longitudinal axis of the shaft such that the plurality of loopelements has an axial reach both proximal and distal the distal end ofthe shaft.

In some embodiments, each of the plurality of loop elements includes atleast one shape memory wire and one radiopaque wire.

In some embodiments, the shape memory wire is made of a nickel titaniumalloy and the radiopaque wire is made of platinum.

In some embodiments, the loop elements in the fully deployedconfiguration are arranged to form a circle geometry when viewed alongthe longitudinal axis.

In some embodiments, the object being retrieved by the device is afilter having a retrieval element and a support member, and wherein theaxial reach of the loop elements in the fully deployed configuration isless than the distance between the retrieval element and the supportmember.

In some embodiments, the proximal portion of the sheath and the proximalportion of the shaft are connected with a snap fitting.

In some embodiments, the proximal portion of the outer sheath and theproximal portion of the inner sheath are connected with a snap fitting.

In some embodiments, the device further includes an outer sheath,wherein the sheath is disposed within the outer sheath.

In some embodiments, the outer sheath has greater column strength thanthe inner sheath.

In some embodiments, the loop elements have a plurality of deploymentconfigurations, and wherein the proximal portion of the shaft includes aplurality of indicators that correspond to the plurality of deploymentconfigurations.

In some embodiments, the plurality of indicators includes a plurality ofdetents.

In some embodiments, the proximal portion of the sheath includes a firsttactile identifier and the proximal portion of the shaft includes asecond tactile identifier, wherein the first tactile identifier isdifferent from the second tactile identifier.

In some embodiments, the at least one deployed configuration includes aninitial deployed configuration in which the plurality of loop elementsare deployed substantially transversely with respect to the longitudinalaxis.

In some embodiments, the plurality of loop elements is deployed in aclover leaf configuration in the initial deployed configuration.

In some embodiments, the at least one deployed configuration includes anintermediate deployed configuration in which the plurality of loopelements are deployed substantially axially with respect to thelongitudinal axis.

In some embodiments, a method for capturing an object in a lumen definedby a lumen wall is provided. The method includes advancing a sheathwithin the lumen, the sheath having a proximal end and a distal end,until the distal end of the sheath is proximal the object; deploying aplurality of loop elements of a snare out of the distal end of thesheath in a propeller-like configuration; and capturing a portion of theobject with at least one of the plurality of loop elements.

In some embodiments, the method further includes withdrawing the loopelements in a proximal direction to engage the portion of the object.

In some embodiments, the method further includes rotating the loopelements to engage the portion of the object.

In some embodiments, the method further includes retracting the portionof the object within the sheath.

In some embodiments, the method further includes advancing an outersheath over the object.

In some embodiments, the method further includes advancing the snare toa full deployment detent on the snare.

In some embodiments, the method further includes visualizing the snarein the lumen using fluoroscopy.

In some embodiments, the method further includes decoupling a snapfitting holding together the sheath and the snare.

In some embodiments, the method further includes decoupling a snapfitting holding together the outer sheath and the inner sheath.

In some embodiments, a device for retrieving an object from a lumen isprovided. The device can include a sheath configured to fit within thelumen, the sheath having a proximal end, a distal end and a radiopaquemarker offset from the distal end. A snare can be disposed within thesheath, the snare having a shaft with a longitudinal axis, a proximalend and a distal end and a plurality of loop elements in connection withthe distal end of the shaft. The plurality of loop elements can have acollapsed configuration within the sheath and at least one deployedconfiguration outside the sheath. The plurality of loop elements can beconfigured to be deployed through an opening at the distal end of thesheath. At least one deployed configuration can include an initialdeployed configuration in which the plurality of loop elements isdeployed substantially transversely with respect to the longitudinalaxis.

In some embodiments, the plurality of loop elements are deployed in aclover leaf configuration in the initial deployed configuration.

In some embodiments, the plurality of loop elements are deployed in anelliptical or oblong configuration in the fully deployed configuration.

In some embodiments, the at least one deployed configuration includes afully deployed configuration in which the plurality of loop elements aredeployed in substantially circular configuration.

In some embodiments, the radiopaque marker is offset about 3 to 5 mmfrom the distal end of the sheath.

In some embodiments, a specific radiopaque marker pattern is disposed oneach of the loop elements to enable visual differentiation of each loopelement fluoroscopically. For example, each loop element can have adifferent number of radiopaque markers.

In some embodiments, a method for capturing an object in a lumen definedby a lumen wall is provided. The method includes advancing a sheathwithin the lumen, the sheath having a proximal end and a distal end,until the distal end of the sheath is proximal the object; deploying aplurality of loop elements of a snare out of the distal end of thesheath until the loop elements achieve substantially full appositionwith the circumference of the lumen wall; and capturing a portion of theobject with at least one of the plurality of loop elements.

In some embodiments, the method further includes aligning a radiopaquemarker offset from the distal end of the sheath with a radiopaquefeature of the object.

In some embodiments, the radiopaque feature of the object is a retrievalelement.

In some embodiments, a device for retrieving an object from a lumendefined by a lumen wall is provided. The device can include a sheathconfigured to fit within the lumen, the sheath having a proximal end anda distal end; and a snare slidably disposed within the sheath, the snarehaving a shaft with a longitudinal axis, a proximal end and a distal endand a plurality of loop elements in connection with the distal end ofthe shaft, wherein each of the plurality of loop element has a proximalportion and a distal portion, wherein the plurality of loop elements hasa collapsed configuration within the sheath and at least one deployedconfiguration outside the sheath, wherein the plurality of loop elementsare configured to be deployed through an opening at the distal end ofthe sheath, wherein the at least one deployed configuration includes afully deployed configuration in which the plurality of loop elements aredeployed such that the distal portions of the loop elements are arrangedin a substantially continuous, circumferential, planar and oblongconfiguration that is transverse to the longitudinal axis.

In some embodiments, the sheath includes a flexible distal tip portionthat is configured to invert when the object is withdrawn into thesheath.

In some embodiments, the plurality of loop elements in the fullydeployed configuration are angled less than 90 degrees with respect tothe longitudinal axis of the shaft such that the plurality of loopelements has an axial reach both proximal and distal the distal end ofthe shaft.

In some embodiments, each of the plurality of loop elements includes atleast one shape memory wire and one radiopaque wire. In someembodiments, the shape memory wire is made of a nickel titanium alloyand the radiopaque wire is made of platinum.

In some embodiments, the proximal portions of the plurality of loopelements comprise spoke portions that are secured together with aflexible sleeve.

In some embodiments, the object is a filter having a retrieval elementand a support member, and wherein the axial reach of the loop elementsin the fully deployed configuration is less than the distance betweenthe retrieval element and the support member.

In some embodiments, the proximal portion of the sheath and the proximalportion of the shaft are connected with a snap fitting.

In some embodiments, the device further includes an outer sheath,wherein the sheath is disposed within the outer sheath.

In some embodiments, the outer sheath has greater column strength thanthe sheath.

In some embodiments, the loop elements have a plurality of deploymentconfigurations, and wherein the proximal portion of the shaft includes aplurality of indicators that correspond to the plurality of deploymentconfigurations. In some embodiments, the plurality of indicatorscomprise a plurality of detents. In some embodiments, the proximalportion of the sheath includes a first tactile identifier and theproximal portion of the shaft includes a second tactile identifier,wherein the first tactile identifier is different from the secondtactile identifier.

In some embodiments, the at least one deployed configuration includes aninitial deployed configuration in which the plurality of loop elementsare deployed substantially axially with respect to the longitudinalaxis.

In some embodiments, the distal portions of the plurality of loopelements in the fully deployed configuration are configured to achievecomplete circumferential apposition with the lumen wall. In someembodiments, the lumen wall can define a lumen that is oblong orcircular or that changes between oblong and circular.

In some embodiments, the at least one deployed configuration includes anintermediate deployed configuration in which the plurality of loopelements are deployed substantially transversely with respect to thelongitudinal axis.

In some embodiments, a device for retrieving an object from a lumen isprovided. The device can include a sheath configured to fit within thelumen, the sheath having a proximal end, a distal end and a radiopaquemarker offset from the distal end; and a snare disposed within thesheath, the snare having a shaft with a longitudinal axis, a proximalend and a distal end and a plurality of loop elements in connection withthe distal end of the shaft, wherein the plurality of loop elements hasa collapsed configuration within the sheath and at least one deployedconfiguration outside the sheath, wherein the plurality of loop elementsare configured to be deployed through an opening at the distal end ofthe sheath, wherein the at least one deployed configuration includes aninitial deployed configuration in which the plurality of loop elementsare deployed substantially transversely with respect to the longitudinalaxis.

In some embodiments, the at least one deployed configuration includes afully deployed configuration in which the plurality of loop elements aredeployed in substantially circular configuration.

In some embodiments, the radiopaque marker is offset about 3 to 5 mmfrom the distal end of the sheath.

In some embodiments, the at least one deployed configuration includes afully deployed configuration in which the plurality of loop elements aredeployed in substantially oblong configuration.

In some embodiments, the plurality of loop elements each includes a loopcollapse facilitator.

In some embodiments, the plurality of loop elements are secured togetherwith sleeves.

In some embodiments, a method for capturing an object in a lumen definedby a lumen wall is provided. The method can include advancing a sheathwithin the lumen, the sheath having a proximal end and a distal end,until the distal end of the sheath is proximal the object; deploying aplurality of loop elements of a snare out of the distal end of thesheath until the loop elements achieve substantially full appositionwith the circumference of the lumen wall; and capturing a portion of theobject proximate to the lumen wall with at least one of the plurality ofloop elements.

In some embodiments, the method further includes aligning a radiopaquemarker offset from the distal end of the sheath with a radiopaquefeature of the object.

In some embodiments, the radiopaque feature of the object is a retrievalelement.

In some embodiments, the method further includes advancing the distalend of the sheath over the captured object.

In some embodiments, the distal end of the sheath inverts as the sheathis advanced over the captured object.

In some embodiments, a method for capturing an object in a lumen definedby a lumen wall is provided. The method includes advancing a sheathwithin the lumen, the sheath having a proximal end and a distal end,until the distal end of the sheath is proximal the object; determiningthe position of the object within the lumen; deploying a plurality ofloop elements of a snare out of the distal end of the sheath to one of aplurality of predetermined loop element deployment configurations basedon the determination of the position of the object; and capturing aportion of the object with at least one of the plurality of loopelements.

In some embodiments, the plurality of loop elements are deployed to thepredetermined loop element deployment configuration using a deploymentindicator.

In some embodiments, the method further includes advancing an innersheath disposed with the sheath over a portion of the object andadvancing the sheath over the entire object.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features of the invention are set forth with particularity inthe claims that follow. A better understanding of the features andadvantages of the present invention will be obtained by reference to thefollowing detailed description that sets forth illustrative embodiments,in which the principles of the invention are utilized, and theaccompanying drawings of which:

FIG. 1A is an axial view of the distal end of one embodiment of thesnare device, showing the loop elements which substantially form acomplete circle about the axis of the shaft. The edges of each loopoverlap adjacent loops to ensure a substantially continuous circularpattern.

FIG. 1B is a side perspective view of the snare device shown in FIG. 1A,showing the loop elements such that the plurality of loop elements hasan axial reach both proximal and distal the distal end of the shaft.

FIG. 1C is a side cross-sectional view of a stowed snare within both anouter sheath and an inner sheath.

FIGS. 1D-1F illustrate the various deployment stages of the loopelements of one embodiment of the snare. FIGS. 1D and 1E illustrate aninitial deployment stage of the loop elements, while FIG. 1F illustratesan intermediate deployment stage of the loop elements.

FIGS. 1G and 1H illustrate the flexible distal tip portion of the sheathwith a deployed snare (FIG. 1G) and a partially stowed snare (FIG. 1H).

FIGS. 1I-1J illustrate snare embodiments having two loop elements with asubstantially elliptical or oblong fully deployed configuration.

FIGS. 1K-1M illustrate snare embodiments having two loop elements with asubstantially elliptical or oblong fully deployed configuration and aloop collapse facilitator.

FIGS. 1N-1Q illustrate the stages of deployment of an embodiment of asnare with two loop elements.

FIG. 1R illustrates a snare embodiment having two loop elements with asubstantially elliptical or oblong fully deployed configuration, and aplurality of radiopaque markers disposed on each loop in differentpatterns, to differentiate each loop element fluoroscopically.

FIG. 1S is a side view of a snare embodiment having two loop elementswith a substantially elliptical or oblong fully deployed configuration,showing the loop elements having both a distal and proximal reach.

FIG. 1T illustrates a snare embodiment having four loop elements in asubstantially circular fully deployed configuration, and a plurality ofradiopaque markers disposed on each loop in different patterns, todifferentiate each loop element fluoroscopically.

FIG. 1U illustrates another snare embodiment having two loop elementswith a substantially elliptical or oblong fully deployed configurationand a loop collapse facilitator.

FIGS. 1V-1X illustrate another snare embodiment having two loop elementsthat are fastened together at the swage and attached together withsleeves.

FIG. 2A is an end view of an embodiment of a single loop element, usinga single nitinol wire wrapped with a single radiopaque platinum wire.

FIG. 2B is a perspective view of the single loop element shown in FIG.2A.

FIG. 3A is a side view of another embodiment of a single loop on the endof a snare device, to illustrate the relative geometry of the loopelements.

FIG. 3B is an end view of the single loop shown in FIG. 3A.

FIG. 4 is an end view of a loop element and a hypo tube, to illustratethe D shape or pie shape geometry of the loop element features.

FIG. 5A is an end view of an embodiment of a single loop element, usinga plurality of wires which are twisted together to form a strand.

FIG. 5B is a close up view of a portion of the single loop elementstrand shown in FIG. 5A.

FIG. 6A illustrates an embodiment of a single loop element, using aplurality of wires which are braided together to form a strand.

FIG. 6B illustrates a close up view of a portion of the single loopelement strand shown in FIG. 6A.

FIG. 7 is a side view of an embodiment of a snare device using singlewire loop elements, and a steel hypo tube which attaches the loops tothe shaft via a crimp process.

FIG. 8 is a close up view of the snare device shown in FIG. 7, furtherillustrating the steel hypo tube which attaches the loops to the shaftvia a crimp process.

FIG. 9 is a perspective view of the snare device shown in FIG. 7.

FIG. 10 is an end view of the snare device shown in FIG. 7. The viewillustrates how the loops overlap laterally, with the outer perimeterforming a circular shape.

FIG. 10A is an end view of another embodiment of a snare device. Theview illustrates how the loop elements are twisted together laterally,with the outer perimeter forming a circular shape.

FIG. 11 is a side view of an embodiment of a snare assembly, where theloop elements are attached to the shaft element with a wire coil.

FIG. 12 is a side view of an embodiment of the shaft, hypo tube, and asingle loop element for illustrative purposes. The actual snare devicecan have a plurality of loop elements. The view illustrates anembodiment of the loop element wherein the angle of the radius portionof the loop element is typically about 45 degrees from the central axisof the hypo tube component.

FIG. 13 is a side view of an alternate embodiment of the snare devicewhere the shaft is made from a twisted strand, and the loop elementsform a circular shape in a single plane 90 degrees from the axis of theshaft.

FIG. 14 is a horizontal isometric view of the alternate embodiment shownin FIG. 13, illustrating the flat circular shape of the outer perimeterof the snare loops.

FIG. 15 is a frontal angled view of the alternate embodiment shown inFIG. 13, illustrating the circular shape of the snare outer perimeter,as well as the straight portions of each loop overlapping the adjacentloop to form a closed circle with no gaps about the perimeter.

FIGS. 16-19 illustrate embodiments of methods of using any of the snares10 disclosed herein.

FIGS. 20-22 illustrate embodiments of a snap fitting that can be usedwith the snare.

DETAILED DESCRIPTION

As illustrated in FIGS. 1A and 1B, an embodiment of a retrieval device10, such as a snare, includes a primary or main shaft 12, having adistal end 14 and a proximal end 16. At the distal end 14 of the shaft12 is a plurality of loop elements 18. In some embodiments, the device10 can typically have at least two loop elements 18, but can have threeor more loop elements 18. These loop elements 18 are attached proximallyto the distal end 14 of the shaft 12 via a hypo tube component 20, andcan be free and independent at their distal-most ends. In otherembodiments, the distal ends of the loop elements 18 can be fastened orconnected to adjacent loop elements using, for example, loop connectors,as described in more detail below. The loops 18 can be of a polymeric ormetallic material, and are typically radiopaque and flexible.

The loop elements 18 can have a region of overlap 31, with a span L1,between the adjacent loop elements. In some embodiments, L1 can be lessthan about 5, 10, 15, 20, 25, 30, 35, 40 or 45 degrees. In someembodiments, L1 can be between about 0 to 45 degrees, or about 0 to 15degrees. The span of radial or circumferential coverage by each loopelement 18 can be defined by the angle α between the two spoke elements30 of the loop element 18, as shown in FIG. 1A and FIG. 4. In someembodiments, angle α depends on the number of loop elements 18 and theamount of loop element overlap, L1. For example, in some embodiments,angle α can be determined approximately by dividing 360 degrees by thenumber of loop elements and then adding the amount of overlap, L1. Thus,for a four loop element snare embodiment with 10 degrees of overlapbetween each loop element, angle α equals approximately 100 degrees. Fora two loop element snare embodiment with 10 degrees of overlap, angle αequals about 190 degrees. In other embodiments, the radial orcircumferential coverage of the loop elements can be different whilestill providing complete radial or circumferential coverage. Forexample, in a four loop element embodiment with 10 degrees overlap, twoloop elements can have an angle α of about 130 degrees while the othertwo loop elements can have an angle α of about 70 degrees.

The shape and flexibility of the loop elements 18 allows them tocollapse and/or fold down easily into, for example, a 7 Fr or smallersheath catheter 22 during loading of the device 10 into the sheath 22and/or during deployment of the device 10 from the sheath 22 andretraction of the device 10 into the sheath 22, as illustrated in FIG.1C. In some embodiments, an additional outer sheath 36 can be used toprovide additional column strength. In some embodiments, the outersheath 36 can be a braided sheath, while the inner sheath 22 can be acoiled sheath, which can be more flexible that the braided sheath. Theouter sheath 36 can be used with any of the embodiments disclosedherein.

In some embodiments, as illustrated in FIGS. 1G and 1H, the sheath 22,which can be used in a single sheath embodiment or as an inner sheath ina double sheath embodiment, can have a soft, flexible and elastic distaltip portion 32 that can expand over a foreign object, such as a filter40, that is being pulled into the sheath 22. In addition, the flexibledistal tip portion 32 can evert when the foreign object and/or deployedloop elements 18 are retracted back into the sheath 22. When theflexible distal tip portion 32 inverts, it can form a ramp-likestructure that facilitates the retraction of the filter 40 and the loopelements 18 back into the sheath 22. The main portion 34 of the sheath22 can have stiffer column strength than the flexible distal tip portion32 in order to tolerate the relatively high levels of force that can begenerated while pulling out embedded filters with the device 10. In someembodiments, as mentioned above, an outer sheath can be used to provideadditional column strength if needed.

In some embodiments, the distal tip portion 32 of the sheath 22 can beradiopaque and/or include a radiopaque marker. For example, in someembodiments, the polymer forming the distal tip portion 32 can be dopedwith radiopaque elements or compounds, such as barium, tantalum,tungsten, palladium, platinum or iridium based compounds or elements.Alternatively or in addition to the radiopaque doping, a single orplurality of radiopaque markers, such as a radiopaque marker band madeof the radiopaque elements or compounds described herein, can beincorporated into the distal tip portion 32. In some embodiments, theradiopaque marker band can be offset approximately 1-10 mm, or about3-mm from the distal end of the sheath 22, so as to not interfere withthe elasticity and eversion of the distal tip portion 32 during thecapture process. The radiopaque doping and/or marker allow the operatorto visualize the location of the distal tip portion 32 of the sheath 22during insertion, advancement, and positioning of the sheath 22 near theforeign object within the lumen. This allows the operator to accuratelyand precisely advance and position the tip of sheath 22 to the foreignobject. In some embodiments where an outer sheath is combined with theretrieval sheath, each sheath can employ different radiopaque markerpatterns to allow the operator to differentiate between the two sheathsfluoroscopically.

In addition, the marker offset can also function as an alignment featurewhich aids the operator in positioning the distal end of the sheath 22in the proper location relative to the foreign object to be retrieved.For example, the foreign object can be a filter 40 with a frame 52, aplurality of anchors 50 on the frame 40 and a retrieval element 42 asillustrated in FIGS. 16-19. In some embodiments, deployment of the loopelements 18 is ideally distal the retrieval element 42 but proximal theanchor 50 closest to the retrieval element 42, which can be achieved belining up the marker band 54 with an element or feature on the filter40, such as the retrieval element 42, for example. The distance dbetween the retrieval element 42 and the anchor 50 can serve as a designconstraint for loop element 18 deployments, where the loop elements 18can be designed to deploy with an axial reach of less than the distanced between the retrieval element 42 and the anchor 50 or other feature onthe filter 40. FIGS. 16-19 are more fully described below.

In some embodiments, the shaft 12 is straight and can be made ofpolymeric or metallic material, for example. The shaft 12 can be made ofa solid design such as a wire, but can alternatively be hollow tofacilitate passage of secondary devices through a lumen in the shaft 12.The shaft 12 can be of a single wire or element, but can also beconstructed of a plurality of wires or elements which can be braided,twisted or stranded into a single shaft 12. The shaft 12 provides ameans by which the user can advance, manipulate, and retract the distalend 14 of the device to capture and remove a foreign object from thehuman body. Typically, the user manipulates the device 10 at theproximal end 16, which is typically outside of the human anatomy. Bymanipulating the shaft 12, the motion is translated to the distal end 14of the device 10, which in turn causes the loop elements 18 to movewithin the human anatomy. This motion allows the loop elements 18 tocatch on the foreign object to be removed from the body. Consequently,the shaft 12 can be designed to have sufficient stiffness, flexibility,pushability and torqueability to accomplish the functions describedherein. In some embodiments, a single wire shaft can provide sufficientstiffness, flexibility, pushability and torqueability. In otherembodiments, a multiple wire shaft can provide sufficient stiffness,flexibility, pushability and torqueability.

In some embodiments, a hypo tube 20 attaches the loop elements 18 to theshaft 12. The hypo tube 20 has an inner diameter and an outer diameter,and is typically sized such that the shaft 12 and all of the loopelements 18 can fit within the inner diameter of the hypo tube 20. Theinner diameter is sized such that there is adequate interference betweenthe hypo tube 20 and the shaft 12 and the loop elements 18, so that thehypo tube 20 can be swaged or crimped circumferentially, mechanicallylocking the loop elements 18 and shaft 12 together. Additionally, thehypo tube can be radially shaped into a non-circular shape, such as butnot limited to a hexagon or square or other rectilinear shape, tofurther facilitate mechanical fit and locking of said shaft 12 and loopelements 18. In some embodiments, the length of the hypo tube 20 isabout at least two times its outer diameter, but can be as short as onetimes its outer diameter, or as long as twenty times its outer diameter.The loop elements 18 can also be attached to the shaft 12 via welding,soldering, capturing within a coil, or potting within a polymeric orrigid adhesive form, for example.

In some embodiments, the loop elements 18 have a geometric shape whichallows them to deploy in a staged manner, where the shape and effectivediameter of the snare 10 is dependent upon how far the snare 10 isdeployed out of the sheath 22. In a first deployment stage as shown inFIG. 1D, the loops 18 are initially deployed from the sheath 22 andexpand, each with a semi-circular shape, a semi-oval shape, orsemi-oblong shape, for example, and the effective diameter of the snare10 is smaller than the effective diameter when the snare 10 is fullydeployed. In some embodiments such as a four loop elements 18embodiment, the snare geometry in the first deployment stage resembles acloverleaf shape. In some embodiments, as illustrated in FIG. 1E, thecloverleaf shaped loops 18 extend substantially transversely from theshaft 12 and sheath 22. In a second deployment stage as shown in FIG.1F, the loops 18 extend further from the sheath 22. In some embodiments,in the second deployment stage the loops 18 extend both transversely andaxially from the distal end 24 of the sheath 22, thereby providing thesnare 10 with extended axial reach in this configuration. In a thirddeployment stage as illustrated in FIG. 1A, the loops 18 fully expand,reaching the full effective diameter of the snare 10. The snare 10geometry in the third deployment stage can resemble a substantiallycomplete circle, when viewed along the longitudinal axis of the snare 10to yield an end view as shown in FIG. 1A, with spoke elements that leadfrom the circle towards the central hypo tube attachment point. Thecircle geometry created by the radial edge portions of the loop elements18 eliminates or reduces gaps between the loop elements 18, which canmake it easier for the operator to engage a retrieval element on aforeign object with the snare 10, especially when the retrieval elementis located near or around the periphery of the lumen.

To facilitate engagement of the loop elements 18 with the retrievalelement, the loop elements 18, when fully deployed, can be sized toconform approximately to the inner diameter of the lumen in which theforeign object is located. This allows full or substantially fullapposition between the loop elements 18 and the full circumference ofthe lumen wall, which enhances the ability of the snare 10 to capturethe retrieving element. In some embodiments, the geometry of the fullydeployed loop elements 18 can be substantially elliptical, oval oroblong in order to conform to a lumen with a substantially elliptical,oval or oblong cross-sectional geometry. In these embodiments, the majoraxis of the elliptical or oblong geometry can be sized to conformapproximately to the inner diameter of the lumen in which the foreignobject is located. In general terms, the geometry of the fully deployedloop elements 18 can substantially match the geometry of the lumen.

For example, the vena cava may have a generally elliptical or oblongcross-sectional geometry. For use in the vena cava, a snare 10 with loopelements 18 having a substantially elliptical or oblong fully deployedconfiguration can be used advantageously, as shown in FIGS. 1I-1M, whichillustrate snare 10 embodiments having two loop elements 18. In otherembodiments, more than two loop elements 18, such as 3, 4 or more loopelements, can be used. By matching the geometry of the deployed loopelements 18 with the geometry of the lumen, full circumferentialapposition with the lumen wall can be more readily achieved. Inaddition, an elliptical or oblong snare 10, which can have a major axisand a minor axis, can be used in lumens having a wide range of sizesbecause the major axis of the snare can be rotated to provide greaterwall to wall reach when needed. Additionally, the loop elements 18 canexhibit both distal and proximal reach, by forming the shape of saidloops with a proximally biased curve 58, as shown in FIG. 1S. In someembodiments, the distal reach, D3, is up to about 10 mm, and theproximal reach, D4, is up to about 10 mm, where distal reach andproximal reach are in reference to the distal end of the shaft 12. Inother embodiments, D3 and D4 can be greater than or less than the valuesrecited above.

In some embodiments, each individual loop element 18 can employ a singleor plurality of radiopaque markers 56, such that each loop element 18has a different quantity of radiopaque markers 56, or a differentpattern of radiopaque markers 56, to allow the operator to visuallydifferentiate and identify each loop element 18 fluoroscopically, asshown in FIGS. 1R and 1T. For example, as illustrated in FIG. 1R, oneloop element 18 has a single radiopaque marker 56 while the other loopelement 18 has two radiopaque markers 56. Similarly, in FIG. 1T, thefirst loop element 18 has one radiopaque marker 56; the second loopelement 18 has two radiopaque markers 56; the third loop element 18 hasthree radiopaque markers 56; and the fourth loop element 18 has fourradiopaque markers 56.

In some embodiments, the loop elements 18 can be attached or connectedtogether using a variety of techniques, as illustrated in FIGS. 1I and1J. For example, the loop elements 18 can be connected together by loopconnectors 19 which can be made from a piece of wire, metal, plastic orpolymer that can be wrapped, twisted, crimped, molded or formed aroundthe two loop elements 18 at, for example, crossover junctions betweenthe loop elements 18. Other techniques for connecting the loop elements18 together can be used, such as welding or applying adhesives.Alternatively, as shown in FIGS. 1V-1X, the loop elements 18 can beconnected together by loop connectors 19 b which can be sleeves that arewrapped around or otherwise disposed around the adjacent spoke portions30 of the loop elements 18. The sleeves can be made of a variety ofmaterials, such as heat shrinkable flexible plastic tubing through whichthe spokes can be disposed and then secured together by shrinking thetubing around the spokes. For example, the sleeves can be made of PTFEor another biocompatible polymer. The sleeves can provide additionalstructural stability to the loop elements 18 and allow the loop elements18 to be advanced or retracted in unison. Without the sleeves, the loopelements 18 may become separated, with for example one loop elementfacing substantially proximally and the other loop facing substantiallydistally, which makes control of the snare more difficult and also makesvisualization of the snare and object to be retrieved more difficult.Therefore, addition of flexible sleeves, can improve control andvisualization of the loop elements during the retrieval process, whilestill permitting the loop elements to flex and bend and be deployed andmanipulated by the user. Additionally, the spoke portions 30 can betwisted together to attach the loop elements 18 together, as shown inFIG. 10A. For example, the spoke portions 30 of adjacent loop elements18 can be twisted together. Attaching or connecting the loop elements 18together can reduce the likelihood of unwanted or unintentional loopeversion or loop displacement that can occur during loop deployment,loop manipulation within the lumen and loop retraction.

In some embodiments, the loop elements 18 can include a single orplurality of loop collapse facilitator 23 features, as shown in FIGS.1K-1M, that facilitates collapse of the loop elements 18 when the loopelements 18, are retracted back into the sheath 22 or when the sheath 22is advanced over the loop elements 18. The loop collapse facilitator 23can be a preformed crimp or fold in the loop element 18 that serves as acollapse or folding point for the loop element 18 and thereforeinitiates or facilitates collapse of the loop element 18 whencompressive forces are applied to the loop element 18. In someembodiments, each loop element 18 can have at least one loop collapsefacilitator 23.

In addition, the loop collapse facilitator 23 can be oriented in avariety ways. For example, the loop collapse facilitators 23 can bepointed or extend either in a distal direction, as shown in FIG. 1K or aproximal direction (not shown), such that the circumference of the loopelements 18 in the deployed configuration when viewed axially remains inthe same shape, such as elliptical, oval or oblong, as compared toembodiments without the loop collapse facilitators 23, as shown in FIG.1I. In other embodiments, the loop collapse facilitators 23 can bepointed or extend radially inwards as shown in FIGS. 1L and 1M, suchthat the circumference of the loop elements 18 in the deployedconfiguration when viewed axially remains in substantially the sameshape, such as elliptical, oval or oblong, as compared to embodimentswithout the loop collapse facilitators 23, as shown in FIG. 1L. In otherembodiments, the loop collapse facilitators 23 can be pointed or extendradially inwards as shown in the dotted lines in FIGS. 1L and 1M, suchthat the circumference of the loop elements 18 in the deployedconfiguration when viewed axially still remains substantially the sameshape, such as elliptical, oval or oblong, but also includes a radiallyinward indentation, which can be arcuate and taper to a point thatextends radially inwards. The size of the indentation can be controlledby the size of the loop collapse facilitator 23 as well as the shape ofthe taper, as illustrated by the dotted lines and solid linesrepresenting the loop collapse facilitator in FIGS. 1L and 1M. In someembodiments, the loop collapse facilitator 23 can be oriented bothdistally or proximally as well as radially. In some embodiments, theloop collapse facilitator 23 can employ a loop geometry which provides ahinge point to allow the loop element 18 to fold down and collapse withlow force, as shown in FIG. 1U.

FIGS. 1N-1Q illustrate the stages of deployment of an embodiment of asnare 10 with two loop elements 18. As shown in FIG. 1N, during theinitial or first deployment stage, the loop elements 18 extend axiallyout of the sheath 22, thereby providing axial reach to the snare 10 inthis configuration, which is suitable as described herein for guide wireretrieval or pacemaker lead retrieval, for example. More generally, thisconfiguration is particularly suitable to retrieve an elongate objectthat is oriented transversely to the snare axis. In a second deploymentstage, the loop elements 18 change from an axial orientation to atransverse or radial orientation, as shown in FIG. 1O, in which thesnare 10 has little or minimal axial reach. This configuration may besuitable when the space between the retrieval feature or object andanother structure is small and more can more easily be accessed by loopelements with little or minimal axial reach. In the third or fulldeployment stage, as illustrated in FIGS. 1P and 1Q, the loop elements18 are fully deployed, forming a circumference that is shaped to conformto the shape of the lumen, such as circular, elliptical, oval, oblong,or any other suitable shape, as illustrated in FIGS. 1I-1M. In the thirddeployment stage, the snare 10 can have some axial reach and full radialreach which can be configured to provide full circumferential appositionwith the lumen wall. The axial reach in the third deployment stage canbe increased or decreased to enhance capture of the foreign object, suchas a filter, as described herein.

The diameters of the wires can be 0.002″-0.007″ each. The wires can betightly wound together, and then formed into a loop element 18 of thedesired shape. The loop element 18 outer radiused edge portion 26 can beangled such that the span of the radiused edge portion 26 is at angle ofbetween about 45 degrees and 90 degrees, relative to the axis of theshaft 12.

The loop element 18 of one embodiment, as illustrated in FIGS. 2A and 2Bis made of at least two wires, which are tightly gathered in a twistedconfiguration, where at least one of the wires is a shape memory nickeltitanium wire, and at least one of the wires is of a radiopaque platinumwire. In some embodiments, the twisted configuration can be advantageousover the braided configuration, when a specific stiffness property ofthe loop elements 18 is desired, by varying the number of wires and wirediameter used in the strand. In some embodiments, the loop element 18includes 2 shape memory nickel titanium wires and two radiopaqueplatinum wires. Other materials can be used in place of the nickeltitanium and/or radiopaque platinum wires. For example, the nickeltitanium alloy, such as Nitinol, can be replaced with a stainless steelwire or polymeric wire. In addition, the radiopaque wire can be replacedwith another radiopaque material, such as a platinum-iridium wire, apalladium wire, a gold wire, a tantalum wire, a tantalum-tungsten wire,and the like. In addition, these radiopaque materials can beincorporated into polymeric materials directly or a modified form, suchas a salt for example. The radiopaque materials can be bonded orattached to the non-opaque wire in a variety of ways, including wrappingor braiding the radiopaque wire with the non-radiopaque wire together,or by attaching marker bands to the non-radiopaque wire, or by claddingthe non-radiopaque wire with the radiopaque material, for example. Inmany embodiments, the use of various radiopaque markers can be used toindicate the relative location and orientation of the deployed snare 10in the target area.

FIGS. 3A and 3B depict a view of one embodiment, where just one loopelement 18 is shown attached to the shaft 12 for the sake of clarity.The embodiment shown in FIGS. 3A and 3B can have a plurality of loopelements 18, such as two, three, or four loop elements 18, or more thanfour loop elements 18 as described herein. A snare 10 with more loopelements 18 will have more spoke portions 30 that can engage with theforeign object, which may aid in retrieval of the foreign object.However, an increased number of loop elements 18 may obscure real-timeimaging of the snare elements and foreign object, making it moredifficult for the operator to correctly identify all the loop elements18 on the screen, which may interfere with efficient manipulation of thesnare 10. In addition, a snare 10 with too many loop elements 18 can endup having a larger compressed diameter due to the many loop elements 18that are attached to the shaft 12 via, for example, a hypo tube 20 swageconnection, as discussed below. As more loop elements 18 are swaged tothe hypo tube 20, the diameter of the hypo tube 20 increases in order toaccommodate the additional loop elements 20. Increasing the compresseddiameter of the snare 10 is generally undesirable for many minimallyinvasive techniques with which the snare 10 can be used because a largerdevice requires a larger percutaneous incision, which increases the painand recovery time for the patient.

In contrast, in some embodiments a snare 10 with fewer loop elements 18,such as two loop elements 18, can be more easily visualized using realtime imaging techniques, thereby allowing the operator to accuratelyidentify each loop element 18 and therefore efficiently manipulate theposition and orientation of the snare with respect to the foreignobject. The two loop element embodiment, as discussed above, can stillbe capable of achieving complete or substantial circumferentialapposition with the lumen wall. In some embodiments with too few loopelements 18, such as a single loop element, the single loop element canbe too floppy, and a floppy loop element 18 can be difficult toprecisely manipulate and position, making grasping a small retrievalelement on a foreign object more difficult.

FIGS. 3A and 3B illustrate the shape of the loop element 18 from twoangles; a transverse side view in FIG. 3A and a front axial view in FIG.3B. The shaft 12 can be attached to the hypo tube 20 via swaging. Thehypo tube 20 can also be swaged to the loop element 18. The loop element18 can be made from a strand of four wires, two Nitinol wires and twoplatinum wires.

FIG. 4 is an axial view of an embodiment of a loop element 18 and a hypotube 20. The shape of the loop element 18 includes a radiused edgeportion 26 which shares its radial center with the center axis of thehypo tube 20. The radiused edge portion 26 is bounded at each end by aradiused corner feature 28, which transitions the radiused edge portion26 into two straight spoke portions 30. These straight spoke portions 30are typically the radius length from the central axis of the hypo tube20 to the radiused edge portion 26 of the loop element 18. In someembodiments, the straight spoke portions 30 are set at an angle α ofapproximately 90 degrees, and radiate from the central axis of the hypotube 20 to the outer radius of the radiused edge portion 26 of the loopelement 18.

The loop elements 18 have a geometry that enables them to catch easilyon foreign objects in the human anatomy. In some embodiments as shown inFIG. 4, the loop element 18 has a “D” shape which resembles a pie slicewith rounded corners, when viewed axially along the device axis. This Dshape includes a radiused edge portion 26, which shares a radial centerwith the axis of the shaft of the device. The radiused edge portion 26is bounded at either end by a radiused corner portion 28 whichtransitions the radiused edge portion 26 into two straight spokeportions 30. In some embodiments, the radiused corner portion 28 bendsabout 90 degrees towards the central axis of the shaft 12.

In some embodiments, the two straight spoke portions 30, which radiatefrom the central axis of the hypo tube to the outer radius of theradiused edge portion 26, are set at an angle α of about 90 degrees, fora snare 10 with four loop elements 18. In some embodiments, the angle αbetween the two straight spoke portions 30 can be less than 90 degreeswhen, for example, the snare 10 has more than four loop elements 18,such as an angle of about 60 degrees for a snare 10 with six loopelements 18, or an angle of about 72 degrees for a snare 10 with 5 loopelements. To generalize, in some embodiments, the angle in degreesbetween the straight spoke portions 30 can be determined by dividing 360by the number of loop elements 18 in the snare 10. This results in aconfiguration where the loop elements 18 cover an entire circle of spacewhen viewed along the axial axis. Therefore, in an embodiment of thesnare 10 with three loop elements 18, the angle between the two straightspoke 30 portions can be about 120 degrees. In some embodiments, theangle α between the straight spoke portions 30 can be greater than asdetermined using the formula set forth above, which results in anoverlap of portions of the loop elements 18 with adjacent loop elements18. In some embodiments, the angle between the two straight spoke 30portions is greater than the value calculated in the formula set forthabove, where an angle of about 5 to 15 degrees ensures that there isminimal or no gap about the perimeter of the snare, to form a closedcircle.

In some embodiments, from a transverse view, the large radiused edgeportion 26 of the loop element 18 can be angled between about 90 degreesand about 30 degrees relative to the axis of the shaft 12 of the device10, as shown in FIG. 12. This edge can also be substantially or exactly90 degrees from the shaft axis, forming a flat, single plane circle whenviewed transversely, as shown in FIG. 13.

In other embodiments, from a transverse view, the large radiused edgeportion 26 of the loop element 18 can be angled at an angle β that isfrom about 5 to 45 degrees relative to the longitudinal axis L of theshaft 12 of the device 10, as shown in FIGS. 3A and 12. Such aconfiguration where the radiused edge portion 26 is angled less than 90degrees results in a propeller like configuration where the loop element18 has a pitch and axial reach both proximal and distal the end of theshaft 12 and/or sheath 22. As illustrated in FIG. 12, the loop element18 has a portion proximal to the distal most portion of the shaft and aportion distal to the distal most portion of the shaft, as shown by thedotted line which divides loop element 18 into the proximal portion 18Aand the distal portion 18B. In addition, the propeller configuration canresult in the opening of the loop elements 18 being oriented in both aplane transverse to the snare axis and a plane parallel to the snareaxis.

In these embodiments, the axial deployment length at full deployment ofthe loop elements 18 is relatively short when compared to some prior artdevices which resemble the intermediate deployment configurationillustrated in FIG. 1F for some embodiments. A long axial deploymentlength can be beneficial in some situations, such as capturing a guidewire that is oriented generally transversely to the snare 10, orcapturing a retrieval element on a foreign object when the retrievalelement is located at or near the center of the lumen. A short axialdeployment length can be beneficial in other situations, such ascapturing a retrieval element that is located at or near the peripheryof the lumen. In some embodiments, loop elements 18 with a long axialdeployment length can inadvertently capture structural elements on theforeign object, such as frame anchors on a filter, rather than theretrieval element which is specifically designed to be engaged by thesnare. When a structural element such as a frame anchor is capturedinstead of the retrieval element, the filter may not be able to bewithdrawn into the sheath 22 and be removed. In addition, the loopelements 18 may get tangled up with the frame anchors and otherstructural elements more easily when the axial length is long. This canbe a problem with some prior art devices, such as the EN Snare®retrieval device, which has a long axial reach. For at least thesereasons, a short deployment length can be advantageous over a longdeployment length in certain situations. In some embodiments, the axialdeployment length of the loop elements 18 can be less than the distancebetween the retrieval element and the support member or anchor of thefilter, thereby reducing the likelihood that the loop elements 18 willinadvertently engage the anchors on the support members. In someembodiments, the axial deployment length of the loop elements 18 can beless than the distance between the retrieval element and the supportmember crossover or the material capture structure of the filter. Insome embodiments, the axial deployment length of the loop elements 18can be less than the distance between the retrieval element and anystructure on the filter in which the loop elements can get entangledwith or that interfere with the function of the loop elements 18.

In addition to the axial deployment length, loop elements of prior artdevices lack substantially complete circumferential apposition with thevessel wall, which makes it difficult to retrieve objects near theperiphery of the blood vessel lumen. In contrast, embodiments of thesnare disclosed herein achieve substantially complete circumferentialapposition which facilitates retrieval of objections, such as retrievalelements on filters, that are located near the periphery of the bloodvessel lumen.

FIGS. 5A and 5B illustrates an embodiment of a loop element 18 made offour round wires, which are tightly gathered in a twisted configuration,where two of the wires are of shape memory nickel titanium wire, and twoof the wires are of a radiopaque platinum wire. The diameters of thewires can be about 0.004″ each. The wires are tightly wound together,and then formed into a loop shape. In some embodiments, the loop outerradius is angled such that the span of the radius is at angle of betweenabout 45 degrees and 90 degrees, relative to the axis of the shaft.FIGS. 6A and 6B illustrates a similar embodiment of a loop element 18made of four wires, except that the wires are braided together ratherthan twisted together to form the loop element 18.

One alternate embodiment of the device 10, illustrated in FIGS. 7-10,includes a series of loop element structures 18 mounted in asubstantially circular geometry when viewed along the longitudinal axis.In some embodiments, the loop elements 18 extend substantiallytransversely with respect to the longitudinal axis. In some embodiments,the outer circular perimeter defined by the loop elements 18 issubstantially continuous and does not have gaps. In some embodiments,the overlap 31 between the loop elements 18 is as described above forFIG. 1A, where the overlap 31 covers a pie shaped region that extendsfrom the outer circumference of the loop elements to the center wherethe loop elements are attached to the shaft. In other embodiments, theoverlap 31 between the loop elements 18 can change as the loop elements18 are further extended out of the sheath. For example, as shown in FIG.10, the loop elements 18 can have an overlap 31 that occurs overapproximately the middle to distal portion of the loop elements 18. Asillustrated in FIG. 10, the overlap 31 begins at crossover points 33between the spokes 30 of the loop elements 18. In some embodiments, asthe loop elements 18 are retracted back into the sheath, the crossoverpoints 33 move closer towards the center, until the crossover pointsmerge into the center, resulting in an overlap configuration similar tothat illustrated in FIG. 1A. In addition to the variable overlapregions, the embodiment illustrated in FIG. 10 has interior gap portions35 between the loop elements. These interior gap portions 35 extendradially inwards from the crossover points 33, and can decrease in sizeand disappear as the loop elements 18 are retracted back into thesheath. In these embodiments, the loop elements 18 can have a radialspan that can be defined by the angle α, and an overlap with a span L1,similar to that described above for FIG. 1A. In these embodiments and inothers, the overlap portions can also act as additional snaring portionswhich increase the likelihood that a portion of the device engages theobject to be retrieved.

In some embodiments, the loop elements 18 can be attached to a shaft 12via a swaged or crimped hypo tube 20. These loop elements 18 can be madeof two or more wires, including at least one Nitinol wire and at leastone platinum wire. As illustrated in FIGS. 7-10, in some embodiments themost distal part of the device 10 can be the loop elements 18 becausethe device 10 does not have a distally extending control member that canbe found in some prior art devices, such as the grasping devicedisclosed in U.S. Pat. No. 7,753,918. In some embodiments, the presenceof a control member may interfere with retrieval of the foreign object,such as a filter, by getting entangled with the filter, making itadvantageous for some embodiments to not have a distally extendingcontrol member. In some embodiments, the loop elements 18 can be angledor have a pitch with respect to the longitudinal axis.

FIG. 11 illustrates another embodiment of the snare 10 where the loopelements 18 are attached to the shaft 12 with a wire coil 21. In someembodiments, the wire coil 21 can be a separate wire that can be wrappedaround the proximal portions of the loop elements 18. In otherembodiments, the proximal portions of the loop elements 18 can bewrapped around the distal end of the shaft 12 in order to form the wirecoil 21. As additionally shown in FIG. 11, the loop elements 18 canextend axially, or in other words, have an axial depth, D1, that can bebetween about 1 to 10 mm. This axial reach allows loop elements 18 toeffect capture of an object, such as a retrieval element of a filter,via rotation about the longitudinal axis of the snare. In someembodiments, the axial depth, D1, is less than the distance between aretrieval element on a filter and the closest anchor to the retrievalelement, as further described below.

Another alternate embodiment, as illustrated in FIGS. 13-15, utilizes atwisted strand shaft 12 made of four 0.010″ Nitinol wires. This shaft 12is attached to twisted strand loops elements 18 using a hypo tube 20using silver solder, for example. After full deployment, the loopelements 18 form a substantially circular geometry which is in a singleplane typically 90 degrees from the axis of the shaft 12. In someembodiments, as illustrated, the loop elements 18 extend bothtransversely and axially with respect to the longitudinal axis of theshaft 12, forming a cone-like structure with a circular base defined bythe distal edge portions of the loop elements 18. The axial reach, D2,or extension of the circular portion past the distal end of the shaftcan vary and can depend on and be less than, for example, the distancebetween the retrieval element and a particular filter structure, such asan anchor, support member, support member crossover, or material capturestructure of the filter, as further described herein. The axial reach,D2, can be between about 1 to 10 mm. In addition, the loop elements 18can a region of overlap 31 and can have a radial or circumferential spandefined by the angle α, as described above with reference to FIGS. 1Aand 4.

In some embodiments, this design offers several key features andcapabilities, for example:

1. Loop Design

The design of the loop elements allows for deployment in different sizelumens, and can conform to variations in lumen anatomy such as tapering,curvature, and angulations. This conformance feature can also enable thedevice to achieve full radial apposition with the target lumenregardless of lumen diameter or circularity. The loop configurationallows the device to catch a foreign object no matter where the objectis located within the luminal space, since the loops reach full radialapposition within the lumen. The design of the elements allows the snareto fit into a very small guiding sheath, facilitating navigation throughtortuous anatomies. The angled design of the loop radius allows thedevice to have axial reach both distal and proximal to the point wherethe loops are attached to the shaft, enabling the loops to locateforeign objects with minimal forward and backward axial manipulation ofthe device by the user. The non-angled design of the loop radius allowsthe device to have a flat, single plane circle geometry, enabling theloops to locate foreign objects with which may be against the vesselwall or partially embedded in the vessel wall. The loops can be maderadiopaque, which allows visualization of the loop under fluoroscopy.Additionally, each individual loop element can employ a single orplurality of radiopaque markers such that each loop element has adifferent quantity of radiopaque markers, or a different pattern ofradiopaque markers, to allow the operator to visually differentiate andidentify each loop element fluoroscopically.

2. Shaft Design

The diameter and mechanical properties of the shaft, such as tensilestrength, stiffness and/or elasticity, allows the user to manipulate theloops easily, by transferring axial and torsional motion from theproximal end of the device down to the distal end of the device. Thediameter of the shaft allows for it to fit within a small diameterguiding sheath. The diameter of the shaft provides tensile support andstrength to allow for high forces that may be required for removing aforeign object from the human anatomy. The shaft can be either solid orhollow, allowing the passage of devices, such as a guidewire, throughthe shaft. The shaft can be of a single element such as a wire, or aconstruction of a plurality of elements which are braided or strandedtogether. The shaft can be of a radiopaque material, to facilitatefluoroscopic visualization.

3. Hypo Tube Design

The inner diameter of the hypo tube allows the loop wires and shaft wireto fit snugly within the inner diameter, to facilitate mechanicalswaging, soldering, or crimping of said hypo tube, mechanically lockingthe elements together. The outer diameter of the hypo tube providesadequate wall thickness to allow mechanical swaging or crimping of thehypo tube to provide a strong mechanical attachment, without crackingthe hypo tube. The hypo tube can be of a radiopaque material, tofacilitate fluoroscopic visualization. Additionally, the hypo tube canbe radially shaped into a non-circular shape, such as but not limited toa hexagon or square or rectilinear shape, to further facilitatemechanical fit and locking of the shaft and loop elements.

In some embodiments, the fundamental design elements which achieve thesefeatures include, for example: (1) a plurality of loop elements, whichare attached to a shaft via a hypo tube; (2) loops which are designed tobe flexible and radiopaque; (3) loops which can be collapsed within aguiding catheter, and deployed outside of the guiding catheter; (4)loops which can reach full circular apposition within the luminal spacein a human body; (5) loops which are attached to a shaft distally, whichextend laterally towards the wall of the vessel of a human body; (6)loops which are angled relative to the axis of the shaft, typically lessthan 91 degrees and typically greater than 1 degrees; (7) loops whichemploy an attachment that is typically a crimped or swaged hypo tube;(8) a shaft which is attached to the loops; (9) a shaft having adiameter allows it to fit within a small diameter guiding catheter; (10)a shaft which can be either solid or hollow; (11) a shaft made of amaterial which can be polymeric, or can be of a metal such as but notlimited to nickel titanium; and (12) a shaft having a length designed toenable the user to position the loops at a desired location to remove aforeign object from a human body.

In some embodiments, the snare device 10 is designed for placement intoa guiding sheath 22, being advanced through said sheath 22, deployingnear a foreign object located within the human anatomy, capturing saidobject, and removing the object from the human anatomy. The shape of theloop elements 18 allows them to conform to the diameter of the vessel inwhich they are deployed into, allowing easier capture of the foreignbody with less manipulation.

The device 10 enables a user to capture a foreign object located withinthe human anatomy, grasp said object in a controlled manner, andretrieve and remove said object from the human anatomy. Examples offoreign objects which might be removed from the human anatomy includeimplants such as stents, guidewires, leads, filters, and valves, andorganic objects such as kidney stones or calcified emboli. For example,a snare 10 can be used to capture a vena cava filter and pull it into aretrieval sheath 22 for removal from the patient.

FIGS. 16-19 illustrate embodiments of methods of using any of the snares10 disclosed herein. As shown in FIG. 16, the snare 10 can be advancedthrough one or more retrieval sheaths 22 and up to the site of adeployed filter 40, which, for example, can be located within the lumen46 of a blood vessel 48. In some embodiments, the snare 10 can bepre-loaded into a sheath 22 which can be inserted into the patient via aminimally invasive procedure, such as a percutaneous insertiontechnique. In some embodiments, the distal end 24 of the sheath 22 canbe advanced to or proximally to the retrieval element 42 of the filter40. In some embodiments, the distal end 24 of the sheath 22 is advancedjust past, i.e. just distal, the retrieval element 42, taking care toavoid advancing the distal end 24 into the other elements of the filter40, such as the filter portion 44 or anchors 50 on the filter frame 52,which would indicate that the distal end 24 had been advanced too far.In some embodiments, the distal end 24 is advanced to a location distalthe retrieval element 42 and proximal the anchors 50 closest theretrieval element 42. In some embodiments, the sheath 22 includes aradiopaque marker 54 located near the distal end 24 of the sheath 22that facilitates alignment of the distal end 24 with respect to thefilter 40. For example, the operator can align the radiopaque marker onthe sheath 22 with the radiopaque retrieval element 42 of the filter 40under fluoroscopy, which results in the distal end 24 of the sheathbeing correctly positioned for loop element 18 deployment, which in someembodiments as described herein is located between the retrieval element42 and the anchor 50 closest to the retrieval element.

As illustrated in FIG. 17, the snare 10 is then deployed into the vessel48. As described above, deployment of the snare 10 can include threedeployment phases. In some embodiments, deployment of the snare 10 caninclude less than three deployment phases, such as one or two deploymentphases, while in other embodiments, deployment of the snare 10 caninclude more than three deployment phases. FIG. 17 illustrates fulldeployment of the snare 10 into the vessel 48 with the loop elements 18in a propeller-like configuration that provides some axial reach bothproximal and distal to the distal end 24 of the sheath 22. In someembodiments, the axial reach in the distal direction can be less thanthe distance d between the retrieval element 42 and anchor 50, therebyreducing the likelihood that the loop elements 18 become entangled withor caught on the anchor elements 50 of the filter during loop element 18deployment and manipulation. In some embodiments, the distance d can bebetween about 5 to 20 mm The region between the retrieval element 42 andthe anchor 50 forms a zone of action in which the loop elements 18 canbe deployed and manipulated to effect capture of the retrieval element42. In some embodiments, the loop elements 18 can have a pitch like theblades of a propeller such that the openings of the loop elements 18 areoriented in both a plane transverse to the snare 10 axis and a planeparallel to the snare axis. This allows the loop elements 18 to capturethe retrieval element 42 either by moving the loop elements 18 axiallyin a proximal or distal direction or by rotating the loop elements 18about the snare axis. In some embodiments, the loop elements 18 aredeployed distal the retrieval element 42 and proximal the support memberof the filter, such that the loop elements 18 achieve substantialapposition with the full circumference of the lumen wall, which isadvantageous for capturing retrieval elements located near the peripheryof the lumen. The deployed loop elements 18 can be withdrawn orretracted proximally to engage the retrieval element.

FIGS. 18-19 illustrate the loop element 18 engaged with the retrievalelement 42 of the filter 40 and the subsequent collapse of the filter 40into the sheath 22. After the retrieval element 42 is secured, the snare10 is held under tension while the sheath 22 is advanced over the filter40, thereby collapsing the filter 40 into the ID of the sheath 22. Insome embodiments using both an inner sheath 22 and an outer sheath, theretrieval element 42, and optionally a portion of the filter 40, isfirst retracted or pulled into an inner sheath 22, in order to securethe filter 40 to the snare 10 and to prevent or reduce unfurling of thetail portion of the filter 40, before the outer sheath is advanced overthe rest of the filter 40.

As the sheath 22 is advanced over the filter 40, the flexible distal tipportion 32 of the sheath 22 can expand and invert over the filter 40,providing a ramp in which the filter 40 can be drawn into the sheath 22.In some embodiments, the inversion of the distal tip portion 32 can beinitiated by contact with specific structures on the filter, such as theretrieval element and/or anchors on the filter frame. In someembodiments, the snare 10 can be retracted in the proximal directionwhile the sheath 22 is advanced in the distal direction to capture thefilter 40 within the sheath 22. In other embodiments, the snare 10 canbe retracted in the proximal direction while the sheath 22 is heldrelatively immobile, i.e. neither advanced nor retracted, to capture thefilter 40 within the sheath 22. In some embodiments, the entire filter40 can be retracted into or captured by the inner sheath.

Another example is the use of a snare 10 to grasp and extract loosekidney stones from a patient's kidneys. The snare 10 is advanced throughone or more sheaths 22, up to the site of the loose kidney stone. Thesnare 10 is then deployed and engaged with the stone. Next, the snare 10is pulled into the sheath 22, or the sheath 22 advanced over the snare10, drawing the stone into the distal ID of said sheath 22.

As described above, the retrieval system can include a plurality ofdifferent components, such as a guide wire, a snare 10, an inner sheathand an outer sheath 22. The proximal ends of these components aregenerally located outside the patient's body so that the operator canmanipulate each of the components by grasping the proximal portion ofthe components and moving the component in a proximal or distaldirection. Often, the proximal portions or ends of the components are orcan be reversibly secured or fixed to one another in a proximal handleportion, using a rotatable or twist fitting, such as a luer lock, forexample. Because one hand of the operator is often used to manipulatethe component, only one hand is free to disconnect or connect thefittings, which can be difficult to do for a rotatable luer lockfitting. In addition, the twisting or rotation of the twist fitting canlead to unintentional and undesired twisting or rotation of the snaredevice.

Therefore, it would be advantageous to provide fittings that can moreeasily be manipulated with one hand, such as a snap fitting, asillustrated in FIGS. 20-22. The snap fitting 100 comprises a femaleconnector 102 and a male connector 104. In some embodiments, the femaleconnector 102 can have a plurality of flexible latch portions 106 thatdefine an opening 112 and enclose a receptacle 108 that is configured toreceive the male connector 104. For example, the female connector 102can have 2, 3, 4 or more latch portions 106. The distal end of eachflexible latch portion 106 can include a retaining feature 110 thatprojects radially inwards and functions to secure the male connector 104within the receptacle 108. The male connector 104 comprises a distalportion 114 that is configured to fit through the opening 112 and withinthe receptacle 108. The male connector 104 can also include a narrowstem portion 116 that has a diameter less than the diameter of theopening 112. In some embodiments, the distal portion 114 and/or thelatch portions 106 can be tapered towards the outer or inner edge inorder to present an angled surface to the opening 112 that can aid inwidening the opening 112 by pushing apart the latch portions 106.

These snap fittings 100 can be integrated into the proximal ends of thevarious components described herein, and well as other components thatcan be used with the retrieval system. Alternatively, the snap fittings100 can be made into luer lock adaptors, or other connector adaptorssuch as screw adaptors, that allow the operator to convert a luer lockfitting, or other fitting, into a snap fitting, as illustrated in FIGS.20-22. In some embodiments, the device can include an outer catheterwith an outer catheter hub and an inner catheter with an inner catheterhub. The female connector 102 of the snap fitting 100 can include alocking feature 118, such as a luer lock fitting, that allows it toreversibly attach to the inner catheter hub. The outer catheter hub caninclude the male connector 104, which can be integrated into the outercatheter hub as illustrated, or can be reversibly attached as describedabove for the female connector 102. In some embodiments, all thecomponents are locked together during insertion.

In some embodiments, the proximal gripping portions of the componentscan include an indicator that identifies which component the operator isgripping, thereby reducing the confusion that can occur in locating thecorresponding proximal gripping portion for the desired component. Insome embodiments, the gripping portion can include a visual indicator.For example, the different components can have color coded grippingportions, or can be labeled with, for example, an easily read symbol orthe name of the component. In some embodiments, the gripping portion caninclude a tactile indicator that allows the operator to distinguishbetween the different components without having to look at the grippingportions, which allows the operator to maintain visual focus on moreimportant matters, such as real-time imaging of the retrieval systemwithin the patient provided through fluoroscopy. For example, onecomponent can have a smooth gripping portion, another component can havea rough or knurled gripping portion, and another component can have adimpled or ridged gripping portion. Each component can have a differenttactile pattern to provide tactile contrast between the components.

In some embodiments, the snare handle portion can include snaredeployment indicators, such as detents, that allow the operator toeasily identify and achieve the different stages of snare deploymentdescribed above. For example, the operator can deploy the snare usingthe snare handle until the snare handle reaches a first indicator, whichsignifies that the snare is deployed in the first deployment stage. Theoperator can then further deploy the snare using the snare handle untilthe snare handle reaches a second indicator, which signifies that thesnare is deployed in the second or intermediate deployment stage. Thenthe operator can further deploy the snare using the snare handle untilthe snare handle reaches a third indicator, which signifies that thesnare is fully deployed. In some embodiments, there is a snaredeployment indicator for each stage of snare deployment. In someembodiments, the loop elements of the snare have differentconfigurations in each of the different deployment stages as, forexample, described above. For example, deployment indicators can beprovided to allow the operator to deploy the snare in stages asdescribed above with respect to FIGS. 1D-1G and FIGS. 1N-1Q. Asdescribed above, a deployment stage corresponding to loop elementshaving an axial configuration can be particularly suited for retrievalof guidewires, leads, and other objects that are positioned transverselywith respect to the snare axis. The fully deployed configuration can beparticularly suitable for devices that have been designed for retrievalwith the snare, such that markers can be used to align the snare withthe object to be retrieved. In addition, the fully deployedconfiguration is particularly suitable for retrieving objects that arelocated near or proximate the lumen wall.

While described in various embodiments for retrieval of filters andother medical devices and objects, the sheath and snare designs may alsobe used to retrieve other filter devices, other embolic protectiondevices, and other objects. For example, filter devices and otherdevices described in commonly assigned, and concurrently filed U.S.Provisional Patent Application Ser. No. 61/586,661 (Attorney DocketNumber 10253-701.102) is incorporated herein by reference in itsentirety and for all purposes.

It is understood that this disclosure, in many respects, is onlyillustrative of the numerous alternative filtering device embodiments ofthe present invention. Changes may be made in the details, particularlyin matters of shape, size, material and arrangement of various filteringdevice components without exceeding the scope of the various embodimentsof the invention. Those skilled in the art will appreciate that theexemplary embodiments and descriptions thereof are merely illustrativeof the invention as a whole. While several principles of the inventionare made clear in the exemplary embodiments described above, thoseskilled in the art will appreciate that modifications of the structure,arrangement, proportions, elements, materials and methods of use, may beutilized in the practice of the invention, and otherwise, which areparticularly adapted to specific environments and operative requirementswithout departing from the scope of the invention. In addition, whilecertain features and elements have been described in connection withparticular embodiments, those skilled in the art will appreciate thatthose features and elements can be combined with the other embodimentsdisclosed herein.

What is claimed is:
 1. A device for retrieving an object from a lumendefined by a lumen wall, the device comprising: a sheath configured tofit within the lumen, the sheath having a proximal end and a distal end;and a snare slidably disposed within the sheath, the snare having ashaft with a longitudinal axis, a proximal end and a distal end and aplurality of loop elements in connection with the distal end of theshaft, wherein each of the plurality of loop element has a proximalportion and a distal portion, wherein the plurality of loop elements hasa collapsed configuration within the sheath and at least one deployedconfiguration outside the sheath, wherein the plurality of loop elementsare configured to be deployed through an opening at the distal end ofthe sheath, wherein the at least one deployed configuration includes afully deployed configuration in which the plurality of loop elements aredeployed such that the distal portions of the loop elements are arrangedin a substantially circumferential, planar and oblong configuration thatis transverse to the longitudinal axis.
 2. The device of claim 1 whereinthe sheath includes a flexible distal tip portion that is configured toinvert when the object is withdrawn into the sheath.
 3. The device ofclaim 1 wherein the plurality of loop elements in the fully deployedconfiguration are angled less than 90 degrees with respect to thelongitudinal axis of the shaft such that the plurality of loop elementshas an axial reach both proximal and distal the distal end of the shaft.4. The device of claim 1 wherein each of the plurality of loop elementsincludes at least one shape memory wire and one radiopaque wire.
 5. Thedevice of claim 4 wherein the shape memory wire is made of a nickeltitanium alloy and the radiopaque wire is made of platinum.
 6. Thedevice of claim 1 wherein the proximal portions of the plurality of loopelements comprise spoke portions that are secured together with aflexible sleeve.
 7. The device of claim 1 wherein the object is a filterhaving a retrieval element and a support member, and wherein the axialreach of the loop elements in the fully deployed configuration is lessthan the distance between the retrieval element and the support member.8. The device of claim 1 wherein the proximal portion of the sheath andthe proximal portion of the shaft are connected with a snap fitting. 9.The device of claim 1 further comprising an outer sheath, wherein thesheath is disposed within the outer sheath.
 10. The device of claim 9wherein the outer sheath has greater column strength than the sheath.11. The device of claim 1 wherein the loop elements have a plurality ofdeployment configurations, and wherein the proximal portion of the shaftincludes a plurality of indicators that correspond to the plurality ofdeployment configurations.
 12. The device of claim 11 wherein theplurality of indicators comprise a plurality of detents.
 13. The deviceof claim 1 wherein the proximal portion of the sheath includes a firsttactile identifier and the proximal portion of the shaft includes asecond tactile identifier, wherein the first tactile identifier isdifferent from the second tactile identifier.
 14. The device of claim 1wherein the at least one deployed configuration includes an initialdeployed configuration in which the plurality of loop elements aredeployed substantially axially with respect to the longitudinal axis.15. The device of claim 1 wherein the distal portions of the pluralityof loop elements in the fully deployed configuration are configured toachieve complete circumferential apposition with the lumen wall.
 16. Thedevice of claim 1 wherein the at least one deployed configurationincludes an intermediate deployed configuration in which the pluralityof loop elements are deployed substantially transversely with respect tothe longitudinal axis.
 17. A device for retrieving an object from alumen, the device comprising: a sheath configured to fit within thelumen, the sheath having a proximal end, a distal end and a radiopaquemarker offset from the distal end; and a snare disposed within thesheath, the snare having a shaft with a longitudinal axis, a proximalend and a distal end and a plurality of loop elements in connection withthe distal end of the shaft, wherein the plurality of loop elements hasa collapsed configuration within the sheath and at least one deployedconfiguration outside the sheath, wherein the plurality of loop elementsare configured to be deployed through an opening at the distal end ofthe sheath, wherein the at least one deployed configuration includes aninitial deployed configuration in which the plurality of loop elementsare deployed substantially transversely with respect to the longitudinalaxis.
 18. The device of claim 17 wherein the at least one deployedconfiguration includes a fully deployed configuration in which theplurality of loop elements are deployed in substantially circularconfiguration.
 19. The device of claim 17 wherein the radiopaque markeris offset about 3 to 5 mm from the distal end of the sheath.
 20. Thedevice of claim 17 wherein the at least one deployed configurationincludes a fully deployed configuration in which the plurality of loopelements are deployed in substantially oblong configuration.
 21. Thedevice of claim 17 wherein the plurality of loop elements each includesa loop collapse facilitator.
 22. The device of claim 17 wherein theplurality of loop elements are secured together with sleeves.
 23. Adevice for retrieving an object from a lumen, the device comprising: asheath configured to fit within the lumen, the sheath having a proximalend, a distal end and a radiopaque marker offset from the distal end;and a snare disposed within the sheath, the snare having a shaft with alongitudinal axis, a proximal end and a distal end, and a first loopelement and a second loop element in connection with the distal end ofthe shaft, the first and second loop elements having proximal spokeportions and distal arcuate portions, wherein the first and second loopelement have a collapsed configuration within the sheath and at leastone deployed configuration outside the sheath, wherein the first andsecond loop elements are configured to be deployed through an opening atthe distal end of the sheath, wherein the at least one deployedconfiguration includes a fully deployed configuration in which thedistal arcuate portions of the first and second loop elements aredeployed such that the distal arcuate portions are arranged in asubstantially circumferential and planar configuration that istransverse to the longitudinal axis.
 24. The device of claim 23, whereinthe proximal spoke portions of the first and second loop elements extendboth axially and radially in the fully deployed configuration.
 25. Thedevice of claim 23, wherein the distal arcuate portion of the first loopelement is arranged opposite the distal arcuate portion of the secondloop element in a mirror configuration such that the distal arcuateportion of the first loop element forms half of a substantiallycircumferential and planar perimeter and the distal arcuate portion ofthe second loop element forms the other half of a substantiallycircumferential and planar perimeter.
 26. The device of claim 23,wherein the proximal spoke portions of the first and second loopelements are secured together with flexible sleeves that have a proximalend located distal to the shaft and a distal end located proximal to thedistal arcuate portions.
 27. The device of claim 23, wherein the sheathcomprises a flexible distal tip configured to invert when the object isdrawn into the sheath.
 28. The device of claim 27, wherein theradiopaque marker is located proximal to the flexible distal tip. 29.The device of claim 28, wherein the radiopaque marker is offset about 3to 5 mm from the distal end of the sheath.
 30. The device of claim 23,wherein the distal arcuate portions are arranged in a substantiallycircumferential and planar configuration that is oblong.